The purpose of this investigation was to determine the effect of the positions and the molecular weight of surfactant hydrophilic functional groups on the rate of gas absorption. A quiescent unsteady-state absorption apparatus was used with carbon dioxide and water as the absorption system. Three surfactants with hydroxyl groups were selected for study, namely, n-octanol, 4-octanol and lauryl diglycol amide. Preliminary absorption tests were made using pure deionized water to determine the diffusion coefficient for the system. A value of 1.93 ± 0.05 x 10⁻⁵ square centimeters per second was obtained. The absorption tests were repeated with the three surfactant solutions at different concentrations. Then the interfacial resistance for each solution was calculated. The results of the surfactants were compared with each other and were also compared with the results of lauryl diethanol amide previous investigated. The octanol with hydroxyl group at a branched position was found to cause a higher interfacial resistance than those with hydroxyl groups at the end of the hydrophobic chain. It was also concluded that increasing the molecular weight of the hydrophilic group decreased the interfacial resistance. / Master of Science

Call number: LD2668 .T4 1979 D465 / Master of Science

Structure direction in the synthesis of phosphate-based materials (aluminophosphates, AlPOs; magnesiumaluminophosphates, MgAPOs; silicoaluminophosphates, SAPOs; magnesiumsilicoaluminophosphates, MgAPSOs), has been investigated through co-templating synthesis studies supported by molecular modelling. These solids have been characterised by diffraction and solid-state NMR, and their properties in gas adsorption and catalysis have been measured. The parameters in the hydrothermal synthesis of SAPO STA-7, St Andrews porous solid number 7, (SAV), in which the macrocycle 1,4,7,11- tetraazacyclotetradecane (cyclam) and tetraethylammonium (TEA) cations are used as co-templates, were investigated in detail. A new route involving a reversal of the mixing order of reagents leads to the formation of single crystals up to 50 μm with perfect tetragonal prismatic morphology that was not achieved via previous synthetic routes. For the first time in SAPO STA-7, X-ray diffraction locates the tetraethylammonium cation (TEA) in tg.tg. conformation. The synthesis and full characterisation of a novel aluminophosphate structure designated STA-14 (KFI) represents the first example of a designed synthesis of a zeotype. The synthesis route is based on a co-templating approach supported by molecular modelling to design the specific template for one of the two types of cages within the structure. The first, a larger type of cage, also present in AlPO-42 (LTA), is templated by the azaoxacryptand 4,7,13,16,21,41-diaza-1,10-bicyclo[8,8,8]- hexocosane (‘Kryptofix 222’, hereafter K222). The modelled co-template configuration, in this case TEA in the tt.tt configuration, was experimentally observed by X-ray diffraction. Modifying the gel chemistry leads to SAPO and MgAPSO STA-14, which display high pore volumes for N₂ adsorption, similar to those of STA-7 and SAPO-34 (CHA). Furthermore, during these synthetic studies, a novel fully tetrahedrally- coordinated magnesiumaluminophosphate layer phase has been prepared, with a structure of relevance to hypothetical VPI-5 (VFI) type extended structures. Molecular modelling was also applied in another aluminophosphate-based material, that of STA-2 (SAT), to predict a template that could be prepared from inexpensive reagents. Existing routes required the use of expensive quinuclidine as a precursor to the template 1,4-bisquinuclidinium butane. The template suggested by modelling, 1,4-diazabicyclo (2,2,2)octane butane (NC₆H₁₂N⁺-C₄H₈-⁺NC₆H₁₂N), labelled DABCO_C4, templated AlPO STA-2 successfully. Structure characterisation of the as- prepared form of AlPO STA-2 using X-ray synchrotron data suggest the formation of Al- OH-Al units to accommodate the positively-charged template within the neutral framework and a combination of ¹³C, ¹⁴N and ¹⁵N NMR studies have been used to give further details of the template environment in the cages. The gas adsorption behaviour of the stable materials STA-7, STA-14 and STA-2 was evaluated for CO₂. High pressure adsorption (0 to 40 bars) on STA-7 and STA-14 shows similar behaviour due to their structural and chemical similarities. The total uptake of CO₂ for SAPO STA-7 is less than for the zeolite NaX (FAU) (3.4 and 5.2 mmolg -1 respectively at 373 K and 12 bars) but the usable capacity for pressure swing adsorption technology (PSA) between 1 to 20 bar for STA-7 is twice the value for NaX. The affinity of adsorption towards CO₂ and its low uptake at 1 bar made SAPO STA-7 a desirable sorbent for PSA. The zeotype affinity of adsorption for different probe gases is different, CO₂ >> CH₄ > CO, to that for zeolite NaX CO₂ >> CO > CH₄. Low pressure CO₂ adsorption (0 to 1 bar) in STA-7, STA-14 and STA-2 at temperatures between 273 and 303 K demonstrates that the topology and therefore the total free pore volume accessible to the gas molecules is the most important factor in determining the uptake in these solids, but that the composition and distribution of the silicon cations within the framework also has an important effect. For example at 273 K and 1 bar, the uptake of the STA-2 framework in the SAPO form is ca. 2wt% higher than in the AlPO form, but compared with SAPO STA-7, the uptake due to pore volume limitations is 10wt% lower under same conditions. In addition, the high quality of the SAPO STA-7 crystals obtained by the new route made them suitable in collaborations for the direct observation of diffusion of methanol by interference microscopy (IFM) and the study of their crystal growth by combined atomic force microscopy (AFM) and high resolution scanning electron microscopy (HRSEM). The catalytic applications of the STA-7 and STA-14 for the methanol-to-olefins reaction (MTO) and the argon adsorption at 87 K were also performed collaboratively. The results are reported and discussed here in the light of their structure and composition.

Abstract not available

As concerns mount about the rise in atmospheric CO₂ concentrations, many different routes to reduce CO₂ emissions have been proposed. Of these, post-combustion CO₂ capture from coal-fired power stations is often the most controversial, as the CO₂ capture system will remove generating capacity from the grid whereas many of the other solutions involve increasing the generating capacity of the grid with low CO₂-emission plants. Despite this, coal-fired power stations represent a major point source for CO₂ emissions, and if a consensus is reached on the need to reduce CO₂ emissions, a low-cost method for capturing and storing the CO₂ released by these power plants needs to be developed. The overarching goal of this research is to design and develop a novel hollow fiber sorbent system for post-combustion CO₂ capture. To achieve this goal, three objectives were developed to guide this research: i) develop a conceptual framework for hollow fiber sorbents that focuses on the energetic requirements of the system, ii) demonstrate that hollow fiber sorbents can be created, and a defect-free lumen layer can be made, iii) perform proof-of-concept CO₂ sorption experiments to confirm the validity of this approach to CO₂ capture. Each of these objectives is addressed in the body of this dissertation. Work on the first objective showed that fiber sorbents can combine the energetic advantages of a physi-/chemi-sorption process utilizing a solid sorbent while mitigating the process deficiencies associated with using solid sorbents in a typical packed bed. All CO₂ capture technologies--including fiber sorbents--were shown to be highly parasitic to a host power plant in the absence of effective heat integration. Fiber sorbents have the unique advantage that heat integration is enabled most effectively by the hollow fiber morphology: the CO₂-sorbing fibers can behave as "adsorbing heat exchangers." A dry-jet, wet-quench based hollow fiber spinning process was utilized to spin fibers that were 75wt% solid sorbent (zeolite 13X) and 25wt% support polymer (cellulose acetate). The spinning process was consistent and repeatable, allowing for production of large quantities of fibers. The fibers were successfully post-treated with an emulsion-based polymer (polyvinylidene chloride) to create a defect-free lumen side coating that was an excellent barrier to both water and gas permeation. A film study was conducted to elucidate the dominant factors in the formation of a defect-free film, and these factors were used for the creation of defect-free lumen layers. The work discussed in this thesis shows that the second objective of this work was definitively achieved. For the third objective, sorption experiments conducted on the fiber sorbents indicated that the fiber sorbents CO₂ uptake is simply a weighted average of the support material CO₂ uptake and the solid sorbent uptake. Furthermore, kinetic experiments indicate that CO₂ access to the sorbents is not occluded noticeably by the polymer matrix. Using the fiber sorbents in a simulated rapid thermal swing adsorption cycle provided evidence for the fiber sorbents ability to capture the sorption enthalpy released by the CO₂-13X interaction. Finally, a slightly more-pure CO₂ product was able to be generated from the fiber sorbents via a thermal swing/inert purge process.

Membrane separation technology has recently emerged as a potential alternative technique for removing higher hydrocarbons (C₃₊) from natural gas. For economic reasons, membranes for this application should be organic vapor selective materials such as poly(dimethylsiloxane) (PDMS) or poly(1-trimethylsilyl-1-propyne) (PTMSP). These polymers, often called solubility selective polymers, sieve penetrant molecules based largely on relative penetrant solubility in the polymer. The sorption and transport properties in such polymers have been reported previously. However, most studies present only pure gas sorption and transport properties. Mixture properties, which are important for estimating membrane separation performance, are less often reported. In addition, mixed gas sorption and diffusion data in such polymers, to the best of our knowledge, have never been investigated before. This research work provides a fundamental database of mixture sorption, diffusion, and permeation data in solubility selective polymers. Two solubility selective polymers were studied: poly(dimethylsiloxane) (PDMS) and poly(1-trimethylsilyl-1-propyne) (PTMSP). The vapor/gas mixture was n-C4H10/CH4. CH4 partial pressures ranged from 1.1 to 16 atm, and [subscript n-]C₄H₁₀ partial pressures ranged from 0.02 to 1.7 atm. Temperatures studied ranged from -20 to 50 oC. The pure and mixed gas [subscript n-]C₄H₁₀ and CH₄ permeability and solubility coefficients in PDMS and PTMSP were determined experimentally using devices constructed specifically for these measurements. The pure and mixed gas diffusion coefficients were calculated from permeability and solubility data. In rubbery PDMS, the presence of [subscript n-]C₄H₁₀ increases CH₄ permeability, solubility, and diffusivity. On the other hand, the presence of CH₄ does not measurably influence [subscript n-]C₄H₁₀ sorption and transport properties. The [subscript n-]C₄H₁₀/CH₄ mixed gas permeability selectivities are lower than those estimated from pure gas measurements. This difference is due to both lower solubility and diffusivity selectivities in mixtures relative to those in pure gas. Plasticization of PDMS by [subscript n-]C₄H₁₀ does little to n-C4H10/CH₄ mixed gas diffusivity selectivity. Increases in mixed gas permeability selectivity with increasing [subscript n-]C₄H₁₀ activity and decreasing temperature were mainly due to increases in solubility selectivity. Unlike PDMS, the presence of [subscript n-]C₄H₁₀ decreases CH₄ permeability, solubility, and diffusivity in PTMSP. The competitive sorption and the blocking effects significantly reduce CH₄ solubility and diffusion coefficients in the polymer, respectively. However, similar to PDMS, the presence of CH₄ has no measurable influence on [subscript n-]C₄H₁₀ sorption and transport properties. [subscript n-]C₄H₁₀ /CH₄ mixed gas permeability selectivities in PTMSP are higher than those determined from the pure gas measurements. This deviation is a result of higher solubility and diffusivity selectivities in mixtures relative to the pure gas values. Mixed gas permeability, solubility, and diffusivity selectivities in PTMSP increased with increasing [subscript n-]C₄H₁₀ activity and decreasing temperature. The partial molar volumes of [subscript n-]C₄H₁₀ and CH₄ in the polymers were determined from sorption and dilation data. The dilation isotherms of PDMS and PTMSP in mixtures agree with estimates based on pure gas sorption and dilation measurements. The partial molar volumes of n-C4H10 and CH4 in PDMS are similar to those in liquids. In contrast, the partial molar volumes of [subscript n-]C₄H₁₀ and CH₄ in glassy PTMSP are substantially lower than those in liquids. Several models were used to fit the experimental data. For instance, the FFV model, the activated diffusion model, and the Maxwell-Stefan model were employed to describe the mixture permeability data in PDMS. Based on the Maxwell-Stefan analysis, the influence of coupling effects on permeation properties in PDMS were negligible. The dual mode sorption and permeation models were used to describe the mixed gas data in PTMSP. The dual mode permeability model must be modified to account for [subscript n-]C₄H₁₀ -induced reductions in CH₄ diffusion coefficients (i.e., the blocking effect). The FFV model provides poor correlations in PTMSP. There seems to be other factors, besides FFV per se, contributing to the temperature and concentration dependence of diffusion coefficients in PTMSP.

No description available.

Orientador: Sergio Persio Ravagnani / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-16T22:22:20Z (GMT). No. of bitstreams: 1 Armellini_VictorAntoniodeDeus_M.pdf: 4894836 bytes, checksum: 94bbcb586bf0955c10788e44b96533de (MD5) Previous issue date: 2010 / Resumo: A emissão de dióxido de carbono (CO2) na atmosfera, quando realizada em larga escala, é considerada como a mais séria causa de problemas ambientais a nível mundial. Devido à atual conscientização mundial em torno do assunto, as indústrias responsáveis estão reduzindo a emissão mediante a captura do gás, normalmente realizada através da absorção do poluente em solventes específicos. Os equipamentos mais comuns, que permitem o contato entre o gás e o solvente, são as colunas de borbulhamento, spray ou recheio. Porém, seu uso apresenta desvantagens que comprometem sua operação, tais como, formação de espuma e dispersão das fases. Frente às desvantagens existentes nos equipamentos convencionais, foram desenvolvidos os módulos de membrana, considerados equipamentos mais adequados para o contato e captura do CO2 pelos solventes. Devido à ausência de trabalhos em condições operacionais mais realistas utilizando módulos de membrana, o presente estudo buscou realizar a modelagem e simulação do processo de absorção de CO2 em módulos de membrana, utilizando como solventes o 2-amino-2-metil-1-propanol (AMP), dietanolamina (DEA) e metildietanolamina (MDEA). A modelagem matemática foi concebida através da adaptação das equações de balanço de massa, capazes de representar numericamente o processo em estudo. Com a intenção de resolver numericamente as equações foi aplicado o método das diferenças finitas de Crank-Nicholson, por fim, buscou-se a implementação de um algoritmo computacional, baseado em linguagem Fortran, para resolver o problema e simular o processo de absorção química de CO2 em módulos de membrana. Inicialmente as simulações foram conduzidas com o intuito de avaliar a estabilidade do método numérico adotado, quanto ao processo em estudo. Após a constatação da estabilidade do método proposto, foi conduzido um estudo para determinar a quantidade ideal de pontos a serem utilizados na discretização. Os resultados obtidos através da simulação tem um comportamento condizente com valores previstos pela teoria. Finalmente, o processo de absorção foi simulado utilizando AMP, DEA e MDEA, onde se verificou que as maiores taxas de absorção de CO2 foram obtidas com o uso de AMP como solvente reativo / Abstract: The emission of carbon dioxide (CO2), when performed on a large scale, is considered the most serious cause of environmental problems worldwide. Due to the current global awareness around the subject, the industries are responsible for reducing emissions by capturing the gas, usually performed by absorption of the pollutant by specific solvents. The most common equipment, which allow contact between gas and solvent are the bubble, spray or fixed bed columns. However, its use has disadvantages that undermine its operation, such as foam formation and phase dispersion. Due the disadvantages existing in conventional equipment, were developed membrane modules, considered the most appropriate equipment for the contact and capture of CO2 by solvents. Due to lack of work in more realistic operating conditions using membrane modules, this study sought to do the modeling and simulation of the process of absorption of CO2 in membrane modules, using the solvent as 2-amino-2-methyl-1-propanol (AMP), diethanolamine (DEA) and metildietanolamina (MDEA). The mathematical model was designed by adjusting the balance equations of mass, capable to represent numerically the process under study. To solve numerically the equations was applied the method of finite difference Crank-Nicholson, finally, we sought to implement an algorithm based on Fortran, to solve the problem and simulate the process of chemical absorption of CO2 into modules membrane. Initially the simulations were conducted in order to assess the stability of the numerical method adopted. After verifying the stability of the proposed method, we designed a study to determine the ideal amount of points to be used in the discretization. Soon after, the validity of the simulator was verified by comparing its results with values predicted by theory. Finally, the absorption process was simulated using AMP, DEA and MDEA, and the highest rates of CO2 absorption were calculated, with the use of AMP as a reactive solvent / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

Orientador: Sandra Lúcia da Cruz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-17T06:22:43Z (GMT). No. of bitstreams: 1 Azevedo_GeraldoGilvande_M.pdf: 2284902 bytes, checksum: 216506a853501999f43bb1c95f73333a (MD5) Previous issue date: 1996 / Resumo: Absorção é o processo utilizado para a separação de um ou mais componentes de uma corrente gasosa, através do contato com um solvente líquido, podendo ocorrer ou não reação química entre eles.Um dos processos industriais mais importantes é a remoção de dióxido de carbono, utilizando-se soluções aquosas de monoetanolamina. Trata-se de uma reação rápida e o CO2 pode estar combinado sob a forma de íon carbamato, carbonato ou bicarbonato. Processos de absorção com reação química, quando comparados àqueles de absorção física apenas, apresentam dificuldades para o seu projeto. Na realidade, os projetos de empresas de grande porte são verdadeiras "caixaspretas" e, no Brasil, pouco tem sido publicado a respeito. No presente trabalho, apresenta-se a modelagem de uma coluna de pratos perfurados para a absorção de CO2 em soluções de monoetanolamina (MEA) e, através da simulação em computador, calcula-se o número de estágios da coluna necessários para realizar uma dada separação, analisando-se diversos parâmetros envolvidos no processo. / Abstract: Absorption is a process where the componentsof a gaseous stream are separated, through a liquid solvent. The process may be simply physical or being follo ed by a chemical reaction. In industry, one of the most important absorption processes is the remova I of carbon dioxide, by using aqueous solutions of monoethanolamine (MEA). The reaction between CO2 e MEA is considered fast and CO2 can be combined in different ways: carbamate, carbonate or bicarbonate ions. Comparing the design of chemical and physical absorbers, the former is more difficult than laUer. In fact, the designs carried out by large companies are truly "back-boxes". In addition, there is not almost anything published in Brazil about this subject. In this work, we present the mathematical modeling of a perforated-tray column for the absorption of CO2 in monoethanolamine (MEA) solutions. A computer program was developed in order to calculate the number of stages necessary to reach a given specification, as 1611 as the severa I relevant parameters involved in the processo. / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química

Orientadores: Elizabete Jordão, Wander Luiz Vasconcelos / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-07-26T17:41:33Z (GMT). No. of bitstreams: 1 Neves_CeliadeFigueiredoCordeiro_D.pdf: 6279733 bytes, checksum: 0ef1f876a9ab54c6121a14df07295fd6 (MD5) Previous issue date: 2000 / Resumo: Os processos de separação são normalmente responsáveis pelos maiores custos de produção nas indústrias químicas, petroquímicas e correlatas. A aplicação comercial de processos adsortivos de separação de gases conhecidos como PSA ("Pressure Swing Adsorption"), têm tido uma aceitação crescente na indústria, pois eles são mais eficientes e econômicos do que os processos de separação convencionais, para pequenas e médias capacidades de produção. O objetivo deste trabalho é desenvolver uma instalação de separação de gases por PSA para a produção de ar enriquecido na faixa de 25 a 50 % de oxigênio, para aplicação em processos de combustão e oxidação, e construir um modelo que permita descrever o comportamento do processo, levando em consideração três parâmetros de avaliação: a pureza e recuperação do produto e a produtividade do adsorvente. Para alcançar os objetivos propostos foi projetada e construída uma instalação laboratorial de PSA utilizando um adsorvente à base de zeólita 5A. O sistema de automação e controle da instalação consiste de um controlador lógico programável conectado a um microcomputador via sistema supervisório, e a diversas válvulas solenóides e instrumentos de medição de vazão, pressão, concentração e temperatura. O projeto e a construção da instalação exigiram um grande esforço de pesquisa e estudo, e conduziram à fonnação de uma equipe multidisciplinar com especialistas em áreas como processos, materiais, automação e controle, que muito contribuiu para a consolidação da pesquisa. Através da utilização de um planejamento fatorial de experimentos foi possível obter modelos empíricos satisfatórios para a pureza, recuperação e produtividade em função das condições operacionais, com erros médios variando entre 1 % e 4 %. Os resultados dos experimentos e as simulações realizadas mostraram que a instalação desenvolvida é capaz de produzir ar enriquecido a 43 % O2, com uma recuperação de 50 % e produtividade de 0,06 moI O_g.ciclo. A otimização do processo foi facilitada pela utilização de outro parâmetro de avaliação do processo, denominado capacidade separativa, que utiliza conceitos básicos da teoria de cascatas aplicada a separações isotópicas / Abstract: Separation processes account for the major production costs in chemical, petrochemical and related industries. Commercial pressure swing adsorption processes (the so-called PSA processes) have been intensively applied in industry since they need lower energy and are less costly than conventional separation processes for low to medium production rates. This work aims to develop a gas separation unit by the PSA process to produce oxygen enriched air between 25 % and 50 % to be used in combustion and oxidation processes. Another objective is to build a model of the process by which its performance can be evaluated through three parameters: product purity, product recovery and adsorbent productivity. To reach these objectives a PSA unit of laboratory scale was designed and built, that uses a bed filled with a type 5A-zeolite adsorbent. Instruments for measuring flow rate, pressure, concentration and temperatures and solenoid valves were linked to a programmable logic controller. A computer was used for data acquisition and to control the experimental set-up. Great effort of research and study placed for design and construction of the installation required a multidisciplinary team of specialists in many fields like processes, materials, automation and control, which was very helpful to consolidate the present research. Using a factorial design of experiments it was possible to develop appropriate empirical models for evaluating purity, recovery and productivity against operational conditions, with mean errors varying between I and 4%. The experimental results and executed simulations of the process showed that the PSA unit works properly for production of oxygen enriched air at a purity of 43 %, recovery around 50 % and productivity of 0,06 mol Ozlkg.cic1o. The process was optimized by another parameter, called separative capacity, which uses basic concepts of cascade theory applied to isotope separations / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química